The unidentified teen reportedly suffered injuries to his head and chest.
Witnesses also said some of the victims had been ejected from their vehicles.
Three people were injured in a multi-vehicle crash Friday on State Route 60 in Riverside County.
A hiker was airlifted Thursday in the Woodland Hills area after reportedly suffering from a medical issue.
Rescue workers saved a 6-year-old boy in Malibu after the child plunged 40 feet down a waterfall.
A motorcyclist was airlifted to a hospital Sunday after sustaining major injuries in a crash in Idyllwild.
One person was killed and a second severely injured in a two-car crash in northern Los Angeles County.
An off-duty firefighter was hospitalized on Monday after falling from rocks in the Porter Ranch area.
A driver is in critical condition after crashing and overturning his Corvette in Aguanga Sunday morning, a fire department spokeswoman said.
A boy scout master fell 20 feet off a trail Saturday while hiking with his troop in the Angeles National Forest, sheriff’s officials said.
Officials say a young girl, 2 or 3 years of age, was struck by a vehicle in Sunland Thursday afternoon.